In vitreous surgery, the surgeon generally holds a vitrectomy instrument in one hand and either traction sutures, an irrigated contact lens, or a second surgical device in the other hand. While operating, the surgeon must also use a high-powered binocular microscope and frequent repositioning of this microscope is necessary because of its high magnification and small field of view. These repositionings are usually accomplished by a foot operated motorized microscope movement. These foot switches can operate in the X-Y (left-right, in-out) directions as well as focusing and zooming. (See "A New Concept for Vitreous Surgery" authored by Parel, Machemar and Aumayr appearing in The American Journal of Ophthalmology, Feb. 19, 1974.)
However, several disadvantages have been noted in the utilization of these foot switches to operate the X-Y and focus (Z) functions of the microscope. This is due to the fact that it is quite difficult for the surgeon to lift his leg to position his foot on the various foot switches without slightly shifting his body and hand position. In addition, this type of foot switch does not permit simultaneous movement of the microscope in two or three directions. The use of one foot to constantly control the microscope, forces the other foot to operate the various surgical modalities such as the vitrectomy instrument, intravitreal cautery, intravitreal cryothermy, remote suction, and photography equipment, thus prohibiting simultaneous operation of any two of these modalities.